At present, in order to have an indication of the temperature attained inside a cooking container, a measurement is carried out by using thermometers or metallic transducers inserted into the knob of the lid or the handles of the container, so as to obtain an external indication on appropriate displaying devices. However, the temperature sensing devices (thermometers) currently produced and used according to traditional techniques present numerous drawbacks, such as the use of multiple components, the difficulty of performing adjustments or calibrations for their initial setup, the lack of precision and poor reproducibility of the measurements of the system. Other devices already in use are capable of emitting an acoustic signal upon reaching a preset temperature level. They are generally constituted by a system based on the reception and refraction of light beams and photocells operating in combination with an already existing thermometer or bimetallic indicator; as the indicator crosses the range of action of the photocells, a bell is sounded.
Alternatively, some digital measuring systems are used, where an electronic system converts the temperature value measured by a sensor into a numerical index; the circuit may be arranged for the setting up of temperature values, so that upon reaching a certain level of temperature or the corresponding numerical value a bell is sounded.
It is evident, however, that even in the cases mentioned above numerous drawbacks occur, which are related to the poor operating reliability of the electronic devices, especially in relation to considerable temperature excursions, difficult ambient conditions, humidity, dust and dirt.
In the first case, in fact, at least one fixed element of the thermometer, capable of actuating a bell, must be provided on a cooking container, where an electronic device can be provided.
In the second case, it is similarly necessary to provide a temperature measuring device, connected to a controlling circuit and capable of converting the measured data into signals or numbers.